a. Field of Invention
The invention relates generally to vehicle structural design, and more particularly, to the structural design of a vehicle bumper system for maximizing the structural rigidity of the bumper system and concurrently minimizing potential rattling thereof.
b. Description of Related Art
As is known in the art, automobiles include a variety of structural components whose design is governed by a variety of performance factors, some of which are related to maximizing the structural rigidity and minimizing potential rattling of the components. For modern bumper systems used with body-on-frame vehicles, such performance requirements are generally met by use an anti-rattle foam layer taped between an isolator and outer fascia layer, with the isolator being affixed to the vehicle frame. Due to build variations, the foam layer is often used on a need-only basis in certain areas. Moreover, even if the foam layer is uniformly disposed between the isolator and outer fascia layer, build variations in these or other related components can result in unintended gaps and thus undesirable rattling of components.
As readily evident to those skilled in the art, application of the foam layer in a uniform and especially on a need-only basis significantly adds to the manufacturing cost associated with a vehicle. Moreover, any components which may rattle upon delivery to a customer can be ascertained as the build quality of a vehicle.
In the art, U.S. Pat. Nos. 5,108,138 to Kawaguchi, 5,957,512 to Inada and 6,663,150 to Evans are exemplary of other known bumper systems. While these designs aim to maximize the structural rigidity and minimize potential rattling of bumper components, the use and effectiveness thereof is however limited due to the drawbacks discussed below.
For example, Kawaguchi, as illustrated in FIG. 1 thereof, provides for a bumper structure including plastic bumper fascia (58) extending laterally for covering bumper reinforce (34). Bumper fascia (58) includes at its upper rear end portion a grooved portion (60) for fixedly receiving forwardly bent portion (42) of bumper reinforce (34). Bumper fascia (58) includes at its laterally extending middle portion a larger platelike flange (62) and two smaller platelike flanges (64) which are positioned laterally beside larger flange (62). Larger flange (62) has larger base portion (66) formed of an isosceles trapezoidal shape and rectangular smaller portion (68) which has rectangular opening (70) formed therethrough, with opening (70) being sized to receive engaging portion (48) of bumper reinforce (34). Thus whereas Kawaguchi provides a method of attachment of bumper fascia (58) to bumper reinforce (34), from a manufacturing viewpoint, components such as engaging portion (48) and its associated flanges (46, 50) significantly add to the overall manufacturing and design costs associated with a vehicle, as well as the overall design complexity for such components. Moreover, these components must be uniquely designed and manufactured for each particular fascia design, and therefore do not present a cost-effective bumper structure from a design and manufacturing perspective.
Referring next to Inada, FIG. 13 of Inada discloses a bumper assembly having an energy absorbing member for absorbing impact energy. Energy absorbing member (28) is accommodated into bumper face (11) in a position opposed to bumper beam (27) which is fixed onto a vehicle body side. Bumper face (11) and energy absorbing member (28) are integrally fixed to each other by tapping screw (29), and energy absorbing member (28) appears to be adhesively or otherwise fixed to bumper beam (27). Thus whereas Inada provides a bumper attachment which uses tapping screws (29) for attaching bumper face (11) to energy absorbing member (28), this attachment method is however limited in application due to the use of screws (29) provided for preventing rattling of bumper face (11), with potential gaps still present between bumper face (11) and energy absorbing member (28). Further, the attachment of energy absorbing member (28) to bumper beam (27) requires yet a further manufacturing step for assembly of the Inada bumper system.
Lastly, Evans, as shown in FIGS. 2-4 thereof, discloses a bumper with an integrated energy absorber (22) including horizontal upper and lower rails (34) and (35), each having rearwardly-facing U-shaped cross sections. Upper rail (34) defines a large portion of rearwardly-facing recess (25), which is shaped to receive the center tubular section of beam (21). Box-shaped sections (33) are molded along rail (34) at strategic locations and have an upper surface shaped to support vehicle front fascia (36). Legs (35′) extend below lower rail (35) for supporting a bottom of the fascia on a front of the vehicle, and attachment of the fascia by means of screws and the like (see FIGS. 3 and 4). Energy absorber (22) has reinforcing walls (55) with top wall (56) shaped to structurally support portions of a fascia in the area of a vehicle front fender. Thus whereas Evans, in a similar manner as Inada, discloses an attachment method for a bumper fascia, this attachment method is likewise limited in application due to the use of screws (see FIG. 3) for preventing rattling of fascia (36), with potential gaps still present between the fascia and energy absorber (22).
It is therefore desirable to provide a bumper system which provides a cost-effective means for minimizing or eliminating rattling of components, such as the outer fascia and the isolator. It is also desirable to provide a bumper system which is simple to design and manufacture, and which is readily tunable for a variety of bumper designs.